Carburetor



June 3, 1958 c. J. ECKERT ETAL 2,837,071

' CARBURETOR Filed Aug. 22. 1956 2 Sheets-Sheet? INVENTOR.

I I (22 767262? J42iezzd [3 BY 'fzzzez 0230/? ATTORNEY United States Patent CARBURETOR Clarence J. Eckert and Elmer Olson, Rochester, N. Y., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application August 22, 1956, Serial No. 605,594

4 Claims. (Cl. 123-419) The present device relates to an improved automatic.

choke mechanism. More specifically, the invention pertains to an automatic choke mechanism which'responds more-accurately to engine operating temperatures than has heretofore been generally possible and which mechanism at the same time is capable of being completely assembled on the carburetor so as to require no further adjustment when the carburetor is itself mounted upon the engine. f

- It haslong been known in the automatic choke art that the closer the thermostatic element of the automatic choke mechanism could be mounted to the engine the more realistic would be the control of the choke valve.

For the sake of manufacturing convenience and the ability to ship a carburetor in which the temperature and vacuum responsive components of the automatic choke mechanism were properly adjusted, it has become customary to mount the automatic choke mechanism elements in a single housing and mount the latter adjacent the choke shaft. This construction has certain inherent advantages in terms of compactness, ease of adjustment and relatively few number of exposed parts. However, the disadvantage of such a construction is that the thermostatic element is located too far from the engine itself to accurately reflect engine temperature under certain operating conditions. In other words, as so remotely located the thermostat tends to cool more quickly than the engine and thus on restarting a partially warmed engine the automatic choke mechanism frequently adjusts the choke valve for an unnecessarily rich starting mixture.

Various attempts have been made to remedy this situation including mechanisms in which the thermostatic element was itself mounted on a manifold hotspot and suitably linked to the remainder of the automatic choke mechanism. This latter approach reduced the problem of making the thermostatic element more closely responsive to engine temperature. However, in so doing this solution creates another problem which is equally undesirable. With the thermostat mounted directly on the manifold rather than on the carburetor, it is impossible to adjust the setting between the vacuum and temperature responsive components of the automatic choke prior to its installation on an engine. Rather it is necessary; to adjust the mechanism connecting the thermostatic element with the remainder of the automatic choke mechanism after the carburetor is assembled to the engine. The practical difficulty of this approach in addition to slowing down the time of assembling an engine is that there is no uniformity in adjusting the operative relationship between the various automatic choke elements with a resultant wide performance variation between carburetors.

Applicants have solved this problem by providing an automatic choke mechanism in which the temperature responsive element is mounted on the carburetor, thus adjustable in relation to the rest of the automatic choke mechanism at the factory, in a unique way to permit the element to also be disposed within a portion of the manifold and therefore highly sensitive to engine temperature.

The specific mechanism and means by which applicants have achieved this result will now be considered in greater detail.

In the drawings:-

Figure 1, is a partially sectioned elevational view of a carburetor mounted on a manifold and embodying applicants invention;

Figure 2 is a partially sectioned view along the lines 22 showing the thermostatic element and housing in greater detail; and

Figure 3 is a partially sectioned view along line 3--3 of Figure 2.

A carburetor is shown generally at 10 mounted on a pad 12 formed on an inlet manifold 14. The carburetor used for illustrative purposes is of the 4-barrel type as illustrated in copending application Serial No. 264,136 Olson et al., filed December 29, 1951. Accordingly, the details of the carburetor will not be described specifically except insofar as they relate precisely to the present invention. It should also be added that the present invention is in no way limited to any particular type of carburetor but is applicable to any carburetor utilizing an auto matic choke mechanism.

The inlet manifold is provided with an exhaust crossover passage 16. Formed in the upper surface of the manifold adjacent the mounting pad 12 is an upwardly opening cavity or receptacle 18 having lower wall 20 in common with the exhaust cross-over passage 16 and in heat exchanging relation with the latter.

Carburetor 10 includes a float bowl casing 22, a choke casing 24 removably mounted thereon and adapted 'to' tioned copending application. Secured to the outer end of the choke shaft 28 is a lever 34.

The throttle body 26 has formed therein a housing 40 adapted to contain the temperature responsive element of the automatic choke mechanism. As best seen in Figure 2 the housing 40 is preferably closed at the top and has a pintle 42 mounted therein. The thermostatic element is a conventional coiled bimetallic member 41, one end of which is fixed to pintle 42 and the other end of which is free. Also mounted in housing 40, through a bearing sleeve 43, is a rotatable shaft 44 coaxially aligned with pintle 42 and having an L-shaped lever 46 suitably fixed thereon. One end 47 of the lever 46 extends transversely of the housing so as to be engaged by the free end 43 of the thermostatic element 41. i

' A device for adjusting the richness of the combustible mixture is provided'on housing 40 and includes a lever-or plate 48 fixed to pintle 42. An element such as screw 50 is provided whereby, upon being loosened relative to housing 40, plate 48 may be rotated to increase or decrease the tension on thermostatic element 41 to vary the richness of the combustible change. After adjusting the setting of the thermostat, the screw 50 is tightened to fix tween the thermostatic and vacuum responsive components of the automatic choke mechanism may be adjusted and fixed when the carburetor is built and thereafter the carburetor may be shipped for assembly with an'engine without necessitating further adjustment. of this relationship other than by way of setting the normal rich-lean mixture as briefly described above.

Further referring to Figures 1 and 2, it will be seen that will at all times be responsive to true engine temperature and accurately adjust the position of the choke valve so as not to cause an undue enrichment of the combustible change particularly when starting a partially warm engine.

While the invention has been illustrated with the vacuum and thermostatic components of the automatic choke mechanism spatially separated, it would be possible to combine the components in a common housing, like 40, constructed in a way to permit the thermostatic element 41 to project below the throttle body. In this event, it would still be necessary, however, to provide some means for operatively linking the automatic choke mechanism. to the choke operating shaft 28. One advantage of such construction would be to eliminate the separate housings now provided for the vacuum and thermostatic components.

The housing 4t may either be formed integrally with the throttle body 26 or it may be a separate member attached in any convenient way to the throttle body so as to be disposed proximate the cavity 18.

Although convenience now dictates that the cavity 18 and thermostatic element 41 be positioned respectively relative to the manifold and carburetor as shown, these locations are variable to any extent which preserves the basic requirements that the automatic choke mechanism is mounted entirely on the carburetor and further that the thermostatic element projects within a portion of the manifold which closely reflects engine operating temperatures.

We claim:

1. A carburetor of the type which includes a choke valve, a throttle body disposed posteriorly of said choke valve and a mechanism for automatically controlling the choke valve in accordance with engine temperature and manifold vacuum, in which said automatic choke mechanism includes a temperature responsive element mounted within the throttle body and projecting therebelow.

2. An engine including in combination an inlet manifold having a mounting pad formed therein, an exhaust cross-over passage, an upwardly opening cavity adjacent it said mounting pad, said cavity being in heat exchanging relation with said cross-over passage; and a carburetor mounted on said pad, said carburetor having a choke valve, a throttle body adapted to seat upon said mounting pad, and means mounted on said carburetor for automatically controlling the actuation of said choke valve, said means including a downwardly opening housing formed on said throttle body and adapted to coact with said cavity to form a heating chamber, a temperature responsive element mounted in said housing and projecting within the cavity portion of said heating chamber.

3. An engine including in combination an inlet manifold having a mounting pad formed therein, an exhaust cross-over passage, an upwardly opening cavity adjacent said mounting pad, said cavity being in heat exchanging relation with said cross-over passage; and a carburetor mounted on said pad, said carburetor having a float bowl casing, a choke casing mounted on the float bowl casing, a choke shaft rotatably mounted in said choke casing, vacuum responsive means mounted on said choke casing proximate said choke shaft and adapted to open the choke valve as .manifold vacuum increases, a throttle body adapted to seat upon said manifold mounting pad, said throttle body including a downwardly opening housing disposed super-adjacent said manifold cavity and forming therewith a heating chamber, a thermostatic element mounted in said housing and adapted to project within the cavity portion of said chamber, a first lever fixed to said thermostatic element and adapted to rotate therewith in response to changes in engine temperature, a second lever fixed to said choke shaft and a rigid link interconnecting said levers for resiliently urging the choke valve towards a closed position when engine temperature is low.

4. A carburetor comprising a float bowl casing, a choke casing mounted on the float bowl casing, a choke shaft pivotally mounted in said choke casing, a throttle body, engine temperature responsive means mounted on said throttle body and including a housing formed on said throttle body, a pintle mounted in said housing, a coiled thermostatic element fixed at one end to said pintle and so mounted that a portion thereof projects below said throttle body, a shaft rotatably supported in said housing and extending therethrough, and means connecting the free end of said element to said rotatable shaft, and a first lever fixed to said temperature responsive means and adapted to rotate in response to changes in engine temperature, said first lever being mounted for rotation with said rotatable shaft extcriorly of said housing, a second lever fixed to said choke shaft, and a rigid link interconnecting said levers for resiliently urging the choke vallve toward a closed position when engine temperature is ow.

References Cited in the file of this patent UNITED STATES PATENTS 2,143,153 Hunt Ian. 10, 1939 2,334,438 Perrine Nov. 16, 1943 2,421,733 Henning June 3, 1947 

